1. Field of the Invention
The invention relates to a Coriolis mass flowmeter having at least one sensor arrangement, at least one transducer and at least one housing, wherein the sensor arrangement has at least one measuring tube that can be excited to oscillation, at least one oscillation generator and at least one oscillation sensor, wherein the transducer at least in part has the evaluation and power electronics for controlling and measurement evaluation of the sensor arrangement, wherein the sensor arrangement and the transducer are arranged adjacent to one another in a common volume defined by the housing.
2. Description of Related Art
Coriolis mass flowmeters of the type mentioned above are known, for example, from German Patent Application DE 10 2008 007 742 A1. In Coriolis mass flowmeters in general, a measuring tube with a flowing medium is excited into oscillation by an oscillation generator, preferably in a certain eigenform in the resonance frequency. On the input and output sides, inertial forces act differently on the medium flowing in the measuring tube to be excited and, thus, on the measuring tube, so that the deflection of the measuring tube is influenced differently on the input and output sides, and, in this manner, the input and output side oscillations of the measuring tube detected mostly by oscillation sensors arranged at different positions have a phase shift, which is a direct variable for the mass flow of interest and the actual, derived variable to be determined by the evaluation electronics. The transducer, here, also includes the power electronics required for controlling the oscillation generator, wherein the oscillation generator usually consists of electromagnetic actuators, which periodically excite the measuring tubes with flow in resonance frequencies. This operating mode is common in practically all Coriolis mass flowmeters, regardless of whether the sensor arrangement and the transducer are adjacent to one another in a common housing and are arranged in a common volume defined by the housing or whether the sensor arrangement and the transducer—as is normal in most Coriolis mass flowmeters—are arranged in different volumes of different housings.
The more common design of Coriolis mass flowmeters, in which the sensor arrangement and the transducer are implemented separate from one another in different housing volumes, has different advantages that deal with the spatial separation of transducer and sensor arrangement, such as the separate compatibility of the mechanical construction—sensor arrangement—and the measuring device electronics—transducer—and the thermal de-coupling resulting from the spatial separation, in particular from the measuring tubes and the transducer. It should be taken into account, here, that in certain applications in which the Coriolis mass flowmeter is used, there are high medium temperatures and/or high temperature fluctuations, either because the process basically requires such temperatures or because such temperature relations have to be temporarily created, for example, for disinfecting or sterilizing sections of the process, and thus, also of the Coriolis mass flowmeter. Due to the spatial separation of the sensor arrangement and transducer, an electric and magnetic de-coupling between the transducer and the parts of the sensor arrangement relevant to electronics and magnetism, i.e., the oscillation generators, occurs independently of the thermal de-coupling.
Generic Coriolis mass flowmeters are more compact in design and can be designed to be tough due to the closed construction. In these types of Coriolis mass flowmeters, in which the sensor arrangement and the transducer are adjacent to one another in a common volume defined by the housing, as opposed to the above-mentioned construction, the sensor arrangement and the transducer strongly interact due to their relative closeness to one another, which can be a problem, in particular in view of compliance of certain measurement accuracies that are placed, in particular, on Coriolis mass flowmeters of high requirements; in this manner, an accuracy of less than 0.04% from the measurement of the mass flow is often required for Coriolis mass flowmeters.